Some Americans are becoming overeducated for the jobs that are available to them, as data shows more college educated workers are taking low-skill jobs that are clearly below their qualifications.

Take taxi drivers for example. About 15%, or more than than 1 in 7, had at least a bachelor's degree in 2010, according to Bureau of Labor Statistics data.

Compare that to 1970 when less than 1% of taxi drivers had college degrees. And the job description hasn't changed much, if at all, since then.

"A lot of people, particularly people with bachelor's degrees, are getting jobs, but not good jobs," said Richard Vedder, an economist at Ohio University.

In a study released Monday, Vedder shows that about 37% of employed U.S. college graduates are working in jobs that require no more than a high school diploma. Those include jobs like taxi drivers, sales clerks, firefighters and telemarketers. He calls this phenomenon "credential inflation," as the supply of college grads is growing faster than the jobs requiring that level of education.

Vedder argues that an underemployment problem is likely to persist even after the U.S. economy recovers fully from the jobs crisis. He predicts that the number of college grads will grow by 19 million between 2010 and 2020, while the number of jobs requiring that education is expected to grow by less than 7 million.